Warnant, P., Martin, H., & Herbillon, AJ. (1981). Kinetics of the Selective Extraction of Iron-oxides in Geochemical Samples - Association Between Fe and Cu in Acid Brown Soils. Journal of Geochemical Exploration, 15(1-3), 635-644. https://doi.org/10.1016/0375-6742(81)90093-5 (Original work published 1981)